There are many possible causes for this problem. Here are some of the possible causes:

1. You do not have enough privilege to access/write on your own home directory 2. You do not have enough privilege to write on /dev/null3. Invalid DISPLAY variable is set explicitly4. Improper operation of the dtlogin login process

For each cause, you can try the following solutions:

You do not have enough privilege to access/write on your own home directoryWhether the user's home directory is on a local drive or NFS, a user must have write permission in it. Talk to the system administrator to set 6** privilege in the home directory.

You do not have enough privilege to write on /dev/nullChange permission on the /dev/null file to 666.

Invalid DISPLAY variable is set explicitlyFind out where the DISPLAY values is explicitly set and try removing it. DISPLAY value can be set explicitly and still use XDMCP without issue. However, it can easily lead to XDCMP failure if it is not set correctly.

Improper operation of the dtlogin login process.Restart the dtlogin process or try reinstalling it. Before you do this, contact your system administrator.